/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;


import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;

/**
 * Represents a ternary expression, for example: "someCheck()?true:false".
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @since 3.0
 */
class Ternary extends SpelNodeImpl {

    public Ternary(int pos, SpelNodeImpl... args) {
        super(pos, args);
    }


    /**
     * Evaluate the condition and if true evaluate the first alternative, otherwise
     * evaluate the second alternative.
     *
     * @param state the expression state
     * @throws EvaluationException if the condition does not evaluate correctly to
     *                             a boolean or there is a problem executing the chosen alternative
     */
    @Override
    public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
        Boolean value = this.children[0].getValue(state, Boolean.class);
        if (value == null) {
            throw new SpelEvaluationException(getChild(0).getStartPosition(),
                    SpelMessage.TYPE_CONVERSION_ERROR, "null", "boolean");
        }
        TypedValue result = this.children[value ? 1 : 2].getValueInternal(state);
        computeExitTypeDescriptor();
        return result;
    }

    @Override
    public String toStringAST() {
        return getChild(0).toStringAST() + " ? " + getChild(1).toStringAST() + " : " + getChild(2).toStringAST();
    }

    private void computeExitTypeDescriptor() {
        if (this.exitTypeDescriptor == null && this.children[1].exitTypeDescriptor != null &&
                this.children[2].exitTypeDescriptor != null) {
            String leftDescriptor = this.children[1].exitTypeDescriptor;
            String rightDescriptor = this.children[2].exitTypeDescriptor;
            if (leftDescriptor.equals(rightDescriptor)) {
                this.exitTypeDescriptor = leftDescriptor;
            } else {
                // Use the easiest to compute common1 super type
                this.exitTypeDescriptor = "Ljava/lang/Object";
            }
        }
    }

    @Override
    public boolean isCompilable() {
        SpelNodeImpl condition = this.children[0];
        SpelNodeImpl left = this.children[1];
        SpelNodeImpl right = this.children[2];
        return (condition.isCompilable() && left.isCompilable() && right.isCompilable() &&
                CodeFlow.isBooleanCompatible(condition.exitTypeDescriptor) &&
                left.exitTypeDescriptor != null && right.exitTypeDescriptor != null);
    }

    @Override
    public void generateCode(MethodVisitor mv, CodeFlow cf) {
        // May reach here without it computed if all elements are literals
        computeExitTypeDescriptor();
        cf.enterCompilationScope();
        this.children[0].generateCode(mv, cf);
        if (!CodeFlow.isPrimitive(cf.lastDescriptor())) {
            CodeFlow.insertUnboxInsns(mv, 'Z', cf.lastDescriptor());
        }
        cf.exitCompilationScope();
        Label elseTarget = new Label();
        Label endOfIf = new Label();
        mv.visitJumpInsn(IFEQ, elseTarget);
        cf.enterCompilationScope();
        this.children[1].generateCode(mv, cf);
        if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
            CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
        }
        cf.exitCompilationScope();
        mv.visitJumpInsn(GOTO, endOfIf);
        mv.visitLabel(elseTarget);
        cf.enterCompilationScope();
        this.children[2].generateCode(mv, cf);
        if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
            CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
        }
        cf.exitCompilationScope();
        mv.visitLabel(endOfIf);
        cf.pushDescriptor(this.exitTypeDescriptor);
    }

}
